For trace analysis the concentration ratios of analytes to be determined and of sample matrix constituents respectively need to be considered. Special emphasis has to be given, therefore, to sample preparation in order to isolate quantitatively the trace components. In this context, the key-parameter to be optimized is selectivity. Every single step which is necessary for the analysis is amenable for the overall analytical performance. The entire selectivity from sample extraction, clean up, chromatographic separation and detection is investigated with the examples of immediate analytical problems. The actual topics of this research work range from environmental chemistry including the development of procedures for pesticides, polychlorinated biphenyls or polycyclic aromatic hydrocarbons to chemical pharmaceutical or bioanalytical chemistry. The analytical techniques involved into these studies are: various extraction techniques, total evaporation headspace analysis, fractionation by liquid-liquid partition, adsorption- and high performance liquid chromatography, chromatographic detection principles, infrared spectroscopy etc.